On/off fluid control valves in which a valve member selectively engages a valve seat to block flow between an inlet and outlet passage have been well known for over the last century. Such valves are common in today's home appliances particularly as water shut-off valves in washing machines, refrigerator ice maker valves, and in commercial vending valves.
One appliance valve of this general type is shown in the McCarty, Jr. et al., U.S. Pat. No. 3,672,627.
Presently many water control or shut-off valves include a valve body with a reciprocating valve member therein actuated by a coil drive armature. The valve member usually has an elastomeric seat that engages and seats on a valve seat frequently formed integrally in the valve body. As the valve member moves through literally thousands of cycles, the valve seat in the valve body, which is rigid, causes permanent deformation and wear on the elastomeric seat on the valve member. Because the valve member is frequently not precision mounted within the valve body, small lateral movement of the valve member, i.e. movement laterally with respect to its axis of reciprocation, cause the elastomeric seat to frequently seat on the valve body seat slightly offset with respect to this annular permanent deformation in the elastomeric member causing an incomplete seal permitting the valve to leak when in its closed position.
Another problem in these appliance-type shut-off valves is that they require a higher opening force than necessary and hence, need a coil having more expensive copper content coils. The high opening force requirement is because inlet fluid pressure tends to shut the valve and hence the opening force F is equal to system pressure times the outlet area on the seat in the valve body. For example, if system pressure is 100 p.s.i. and valve outlet diameter 0.084 inches, then the armature force required would be 0.554 pounds.
It is the primary object of the present invention to ameliorate the problems noted above in shut-off valves.